Abstract/Summary

Understanding how parental expenditure reflects food availability and influences reproductive output is a key part of studies of breeding performance. Provisioning behaviour is an important aspect of parental expenditure. We show that Macaroni Penguins Eudyptes chrysolophus have clear sex-specific differences in provisioning behaviour. Females provision chicks throughout rearing and at higher rates than males, which only participate in the later stages. Female provisioning is consistent throughout chick-rearing and appears to relate to a threshold rate governing whether or not chicks survive. The additional expenditure by males (but not females) during the creche period influenced chick growth and fledging mass of survivors. We suggest a very simple model to account for these sex-specific differences and effects. Interannual variation in parental expenditure resulted in differences in reproductive output between years. Years of lowest expenditure resulted in lowest growth rate of chicks, Sex-specific differences in provisioning were similar among years, however, with a consistent proportion of expenditure by males.